Wireless signaling system



Jul 15, 1924, 150mm E. F. \N. ALEXANDERSON WIRELESS SIGNALING SYSTEM Original Filed April 30, 1914 2 Sheets-$heei 1 Fig.1.

Witnesses Inventor-"z {M Q 7% V Ernst Fwal'lexander-son His ttomel July 15 {1924. 1,501,830

E. F. W. ALEXANDERSON WIRELESS SIGNALING SYSTEM Original Filed April 30, 1914 2 s wshem 2 Witnesses: Inventor":

. Ernst F. W.Jq|e an er'so n; I 5 I b5 W His titorneg.

Patented July 15,. 1924.

UNITED STATES PSVATENT OFFICE.

ERNST F. W. ALEXANDEBSON, F SGHENECTAIDY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A GQRPORATION OF NEW YORK.

WIRELESS SIGNALING SYSTEM.

Application fil ed April 30, 1914, Serial No. 835,433. Renewed February 29, 1924.

T 0 all whom it may concern:

Be it known that I, Enns'r F. W. ALEX- ANDERSON, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Wireless Signaling Systems, of which the followin is a specification.

y present invention relates to wireless signaling systems and more particularly to a method of and means for transmitting signals. While inthe description which follows I have shown its application to telephony, it is ada ted for use for transmitting other forms 0 signals as well.

In a previous U. S. Patent N 0. 1,042,069, issued to me on October 12, 1912, I have described and claimed a system of wireless signaling in which comparatively large amounts ofenergy may be controlled by the feeble currents produced by sound waves in an ordinary telephone transmitter. By the present arrangement a similar efi'ect may be secured, but by the employment of a different type of apparatus for producing the desired result.

In carrying my invention into effect I make use, as in the above mentioned patent, of a source of continuous current pulsations or oscillations of high frequency operatively connected to an antenna and vary the amplitude of the current flowing in the antenna from said source in accordance with the signals to be transmitted.

In the system described in the patent I make use of a vapor electric device which is periodically rendered conductive by means of an exciting voltage which is varied in such a way that the period of time is varied during which the device is rendered conductive. As the amount of energy which will pass through the vapor device is dependent upon the length of the period during which it is conductive the amount of energy transmitted to the antenna may be varied in accordance with the amplitude of the exciting Waves. In the present case however I make use of a device which preferably has a unidirectional conductivity at all times and by varying its conductivity vary the amount of energy transmitted to the antenna, Apparatus embodying the necessary qualities for controlling large amounts of energy in this way may be constructed in many different forms. In the type which I have described in the disclosure which follows it takes the form of what I term a relay or electron discharge device comprising an exhausted envelope containing at least two electrodes and a conducting body or current controlling member in proximity thereto, one of the electrodes being provided with means for causing it to emit electrons. A device of this nature when connected toa source of current operates selectively in such a manner as to allow current to fioW between the electrodes in only one direction; that is, there will be a h flow of negative electricity from the electron emitting electrode to the other electrode or electrodes, but no flow in the opposite direction. By the term electron discharge device or electron discharge relay, as used in this specification and the claims which follow, I mean a device, the operating current of which is carried entirely by means of electrons independently of gas ionization.

If a positive potential is applied to the conducting body in proximity to the electrodes in such a device the flow of current will be increased, and if a negative potential is applied thereto the flow of current will be impeded. If the negative potential is made great enough the flow may be stopped altogether. In other words, the amount of current flowing between the electrodes may be varied by varying the electrical field in their vicinity. This effect may be produced either by varying the electrostatic field in the manner described or by varying the electromagnetic field.

By connecting the source of current pulsations or oscillations to such a relay as well as to the antenna the amplitude of the current flow in the antenna may be made de pendent upon the current flow through the relay. The current flow through the relay may in turn be controlled by varying the potential of the current controlling member therein in accordance with current variations produced by the signals which it is desired to transmit. Such an arrangement possesses the important advantage that very small variations in the current derived from the signal producing means and correspondact ingly small variations in the electrical field of the relay are capable of producing much greater variations in the current flow through the relay.

My invention will be best understood by reference to the accompanying drawing in which Figs. 1 to 6 illustrate as many different ways in which it may be carried into effect.

As illustrated in Fig. 1, an antenna 1 for transmitting the signals is connected to earth through the usual adjustable condenser 2. The local source of energy for producing the signals is represented by an alternating current generator 3 which should have a frequency much beyond the range of audibility, although other convenient sources of high frequency alternating current may equally well be employed. The circuit to which the source of energy is connected comprises the usual oscillation transformer 4 for transmitting the signals to the antenna and a second air core transformer 5, preferably so designed as to give a comparatively large secondary voltage. The secondary circuit of transformer 5 includes two relays 6 and 7. As illustrated here these relays comprise cathodes 8 of filamentary form, late shaped anodes 9 and intervening grid s aped conducting bodies 10, within a highly evacuated envelope. Local batteries 11. are provided for heating the cathodes to cause them to emit electrons.

One terminal of the secondary of transformer 5 is connected to the anode of relay 6 and the cathode of relay 7, while the other terminal is connected to the cathode of relay 6 and the anode of relay 7 Although apparatus of this type permits of the passsage of current in but one direction it will be seen that by the present arrangement means is provided for the passage of both half waves of the alternating current through the secondary circuit. The amount of current which will flow through the relays, however, may be varied by a variation of the potential of the grid shaped bodies 10. There isa certain definite potential at which the greatest sensitiveness of the relay occurs. The value of this potential depends largely upon the design of the particular relay used and may easily be determined by experiment. In order to provide the potential desired a battery 12 of the proper strength and polarit is connected to each of the grids 10. ith the arrangement thus far described it will be seen that a high frequency current of a certain definite amplitude will flow in the secondary circuit of transformer 5, and that the current communicated to antenna 1 will also have a definite amplitude depending on the amplitude of the current flowing in the secondary circuit of 5. By varying the potential of the grids 10 corresponding variations may be produced in the antenna current and such variations may be used to transmit signals of any desired character. In order to transmit sound by this means I have shown an ordinary microphone transmitter 13 provided with a local circuit containing a battery 14. It will be understood, of course, that the transmitter may be at a distance from the sending station and conn-ected thereto by a transmission line. This transmitter circuit is inductively connected to the grids 10 by means of the transformers 15 whereby variations in the current produced by sound waves produce corresponding variations in the grid potential and these potential variations in turn produce corresponding variations in the amplitude of the antenna current. As a result the antenna current waves instead of having a constant amplitude will vary in direct proportion to the variation in the current produced by the sound waves. This variation in the transmitted waves may, by appropriate receiving devices, be utilized to reproduce the sound waves at a distant point.

In Fig. 2 I have shown a modification which is the equivalent of the arrangement of Fig. 1 but in which a single relay 16 is employed. The relay in this case has a single cathode 17, two anodes 18 and two interposed grids 19*. The middle point of the secondary of transformer 5 is connected to the cathode 17 and the ends of the secondary are connected to the anodes 18. With this arrangement one-half wave of current in the secondary circuit will flow between the cathode and one of the anodes while the opposite half wave will flow between the cathode and the other anode. The variations of potential produced by variations in the local circuit of the microphone transmitter 13 may be impressed upon the grids 19 by means of a single transformer 20, the middle point of the secondary of which may be connected to the cathode as shown. In a relay of this type it will usually be found desirable to employ an extra grid 21 surrounding the cathode 17 and impress thereon a constant positive potential from a battery 22 as indicated.

With the arrangement shown in Figs. 1 and 2 the amount of energy which may efiiciently be controlled by the relays is limited by the amplitude of the current variations which may be produced by the transmitter 13 in the local circuit. In case it is desired to transmit sound to a greater distance than is possible with the amount of energy which may be controlled by the relays as shown, I may employ another relay to amplify the variations in the speech current as indicated in Fig. 3. In this case a relay 23 similar to those in Fig. 1 may be used. The potential of the grid 10 varies with the variation in the resistance of the transmitter 13 and this IOU produces corresponding variations of much greater amplitude in the current flowing between' the cathode 8 and the anode 9 from the local source of energy 24. These current variations are caused to produce variations in the potential of the grids 19 by means of the transformer 20 as in the arrangement of Fig. 2.

In Fig. 4 I have indicated a greatly simplified arrangement whereby signals of the same character as those already described may be transmitted. I have shown a single relay 25 which may be like those used in Fig. 1 but in this case the source of high frequency current 3 is connected directly in the relay circuit. With this form of my invention current waves will pass through the relay in only one direction but those half waves which pass through the relay will be varied in amplitude by the current variations produced by the sound waves in the same Way as in the other modifications described.

The source of high frequency current may be connected directly in the antenna circuit as shown in Fig. '5. In this case it will usually be found desirable to amplify the varia tions of the current produced by the sound waves by means of a relay 26 which controls the flow of current through the secondary circuit of the transformer 4.

In Fig. 6 another possible modification is shown in which the source of high frequency current is connected in the circuit of the transmitter 13. In this case the potential of the grid 10 varies constantly by reason of the alternating potential connected thereto and corresponding current variations are produced in the relay 27 which has in its circuit a source of energy 28. As a result there will be impressed upon the antenna an alternating current of the same frequency as that of the source 3. The amplitude of this current however will vary in accordance with variations in the potential of the grid 10, which variations in turn may be caused by the variations in the resistance of the transmitter-l3 produced by sound waves.

While, as I have before stated, the devices used for controlling the current flow may assume a variety of forms, in carrying out my invention in the particular way illustrated and described, I have found that it is preferable to exhaust the envelope of the relay to the highest degree possible. If this is done, as high voltages as desired may be applied to the relay and the current flow through the relay will apparently be the result of a ure electron discharge and substantially independent of any as conductivity. By using high voltages in the relay circuit it will be seen that large amounts of energy may be controlled even though the current flow through the relay is comparatively small. I believe however that in case lower voltages are employed in the relay circuit the principle of operation involved may be carried out by means of other forms of apparatus in which there are appreciable amounts of gas or vapor present.

What I claim as new and desire to secure by Letters Patent of the United States, 1s

1. A modulating system comprising an antenna to be supplied with signal waves, means for supplying high frequency power to be modulated to said antenna, an audion having a cathode and anode and an auxiliary electrode, means for serially introducing the impedance between said anode and cathode into said antenna, and means for controlling the potential of said auxiliary electrode in accordance with a signal.

2. A modulating system comprising an antenna to be supplied with signal waves, means for supplying high frequency power to be modulated to said antenna, an audion having a cathode and anode and an auxiliary electrode, means for serially introducing the impedance between said anode and cathode into said antenna whereby all of said high frequency power flows between said anode and said cathode, and means for controlling the potential of said auxiliary electrode in accordance with a signal.

3. In a radio transmission system, an antenna, a source of oscillations connected thereto, an asymmetric thermionic'impedance element effectively in series with said antenna, said impedance element having a cathode, an anode and an impedance controlling element, and means for varying the potential of said controlling element with respect to said cathode to vary the impedance of said thermionic element in accordance with signals.

4. In a system for radio transmission, an antenna, a thermionic cathode and an anode in an evacuated vessel and effectively serially included-in said antenna, an impedance control electrode in said vessel, means for impressing an electromotive force of signal wave form upon said electrode, and means for impressing high frequency power to be modulated upon said antenna.

5. In an electrical transmission system, the combination with a transmission circuit by which energy ,is transmitted directly from one station to another, of a space discharge device having an anode, a cathode and an impedance varying element, said device being so related to said circuit that all of said energy of said transmission circuit passes through said discharge device and means for applying a low signaling frequency electromotive force between said cathode and said impedance varying element.

6. A high frequency circuit by means of which energy is directly transmitted to a distantstaision, an asymmetric thermionic ance of saidi circuit in accordance with sigimpeziance device which is eiiectiveiy in senais. 10 ries arrangement in said circuit, said im- In witness whereof, I have hereunto set pedence device having acathcde, an anode my hand this 29th day of April, 1914.

$121 an impedance controlling element, and ERNST F. WV. ALEXANDERSON. means for varying the potential of said Witnesses:

ccntrciiing element- With respect to said BENJAMIN B. HULL,

cathode is vary the effective series impefi- HELEN 01130121). 

